Not applicable
This invention relates generally to internal fixation means to be adapted to be implanted within the body in direct contact with a bone or bone fragment for the purpose of reinforcement of said bone or bone fragments relative to one another. It relates more specifically to implantable medical devices wherein the internal fixiation means is adapted for positioning vertebrae.
In normal anatomy, the human skeleton is supported by a complex arrangement of ligaments, tendons, joints, and muscles. Congenital disorders, degenerative diseases, malignancies, medical conditions or trauma may cause abnormal conditions. These problems generally cause or allow abnormal displacement or rotation of bones, tendons, or joints. These conditions may require surgical alteration of the existing anatomy.
Fixation of surgical changes is frequently necessary during the healing process because failure to maintain proper alignment between the healing tissues will result in a less than optimal outcome or complete failure of the surgical procedure. Screws and other devices such as plates, hold the bones and tendons in the desired anatomic alignment until healing occurs or the fixation device fails. Loosening of the bone screw from the skeletal bone or from the fixation device is a major contributor to fixation failure. Screw back out and loosening has led to the development of mechanisms for locking the screws in metal plates. These locking mechanism contain intricate components that increase the cost and reduce reliability.
Once healing takes place these fixation devices are no longer needed and may cause complications. If healing does not occur, all fixations with screws and or plates will eventually fail or break.
Improvement of the bone to screw interface is the driving force behind multiple patents and ongoing research for mechanical locks. Bonding is one of the advances toward improving bone to screw interfaces and reducing surgical failure. Simpler more reliable metallic bone fixation systems and methods for the use of polymeric fixation systems are needed. The process and materials of the present patent will improve these fixation systems.
Internal fixation is a temporary means to hold the bones in the proper alignment while the body heals the area with living tissue. Polymers, including bio-absorbable and biodegradable materials will allow the temporary fixation devices to be reabsorbed or incorporated into the patient""s anatomy after healing takes place. These polymers require fixation methods, which will not create stress concentrations in the low strength polymeric screws and plates holding the implants. The present patent provides chemical means, through the use of solvents, glues, or bonding agents, for improving the bone screw interface in polymeric materials without creating stress concentrations.